Supramolecular Coordination Chemistry and Functional Microporous Molecular Materials

Multicomponent self-assembly, wherein two unique donor precursors are combined with a single metal acceptor instead of the more common two-component assembly, can be achieved by selecting Lewis-basic sites and metal nodes that select for heteroligated coordination spheres. Platinum(II) ions show a thermodynamic preference for mixed pyridyl/carboxylate coordination environments and are thus suitable for such designs. The use of three or more unique building blocks increases the structural complexity of supramolecules. Herein, we describe the synthesis and characterization of rectangular prismatic supramolecular coordination complexes (SCCs) with two faces occupied by porphyrin molecules, motivated by the search for new multichromophore complexes with promising light-harvesting properties. These prisms are obtained from the self-assembly of a 90°Pt(II) acceptor with a meso-substituted tetrapyridylporphyrin (TPyP) and dicarboxylate ligands. The generality of this self-assembly reaction is demonstrated using five dicarboxylate ligands, two based on a rigid central phenyl ring and three alkyl-spaced variants, to form a total of five free-base and five Zn-metallated porphyrin prisms. All 10 SCCs are characterized by 31 P and 1 H multinuclear NMR spectroscopy and electrospray ionization mass spectrometry, confirming the structure of each self-assembly and the stoichiometry of formation. The photophysical properties of the resulting SCCs were investigated revealing that the absorption and emission properties of the free-base and metallated porphyrin prisms preserve the spectral features associated with free TPyP. supramolecular chemistry | metallacages T he use of sunlight is ubiquitous as the input for carbonneutral, renewable energy schemes (1). Every strategy that relies on solar energy conversion, ranging from direct conversion to electricity in photovoltaics (2) to the generation of fuels via electrocatalysis (3), photoanode (4, 5), or photocathode devices (6), or photocatalysis (7) requires that photons be absorbed by a molecule or material as the first step in providing the driving force for subsequent transformation. Natural systems have evolved light-harvesting complexes, comprising multiprotein ensembles embedded with pigment molecules to enhance photon absorption for photosynthesis (8). These pigment-rich sites are arranged such that excitation of a distal chromophore will ultimately result in energy transfer to a reaction center via a series of migration and transfer processes (9). Strategies to replicate natural light-harvesting complexes necessarily demand the organization of multiple chromophores (10), a requirement that makes self-assembly and supramolecular chemistry particularly well suited for such efforts (11-13). As such, a variety of approaches have been applied toward the development of new materials that exhibit broadband absorption and efficient energy transfer (14-16). The subsequent studies of such materials span investigations of the fundamental science behind energy migration and transfer, t...

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“…1073/pnas.1408905111/-/DCSupplemental. supramolecular coordination complexes in traditional one-or two-component schemes (50)(51)(52)(53).…”

Section: Significancementioning

confidence: 99%

Synthesis and photophysical studies of self-assembled multicomponent supramolecular coordination prisms bearing porphyrin faces

Shi

Sánchez‐Molina

Cao

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Metal-containing macrocycles with high symmetry and precise architecture are a new class of promising supramolecules for future application in nanotechnology because of their exact shape and size, as well as magnetic, photophysical, and electrostatic properties (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). In this article, we describe scanning tunneling microscopy (STM) studies of the self-assembled supramolecular metallacyclic rectangle, cyclobis[(1,8-bis(transPt(PEt 3 ) 2 )anthracene)(1,4Ј-bis(4-ethynylpyridyl)benzene](PF 6 ) 4 , (Fig.…”

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confidence: 99%

Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

Gong

Wan

Yuan

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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A self-assembled supramolecular metallacyclic rectangle was investigated with scanning tunneling microscopy on highly oriented pyrolytic graphite and Au(111) surfaces. The rectangles spontaneously adsorb on both surfaces and self-organize into well ordered adlayers. On highly oriented pyrolytic graphite, the long edge of the rectangle stands on the surface, forming a 2D molecular network. In contrast, the face of the rectangle lays flat on the Au(111) surface, forming linear chains. The structures and intramolecular features obtained through high-resolution scanning tunneling microscopy imaging are discussed.metallacyclic macrocycle ͉ scanning tunneling microscopy ͉ molecular adlayer ͉ molecular orientation S elf-organization (1) and self-assembly (2) are critical and necessary processes in all living organisms and are of ever increasing importance in chemistry and material science. These processes will play a critical role in the so-called ''bottom-up'' strategy of nanofabrication. Therefore, understanding the organization of molecules on solid surfaces is important, both from a fundamental and applied perspective, for the construction of surface molecular nanostructures and nanodevices (3-13). A self-organized molecular pattern with control of structure and derived concomitant function could provide promising materials for the construction of nanodevices that cannot be prepared by conventional microfabrication. The arrangement of adsorbed molecules onto a surface depends on both intermolecular and molecule-surface interactions. For example, Hipps and colleagues (3, 4) prepared a self-organized 2D bifunctional structure on a Au (111) Metal-containing macrocycles with high symmetry and precise architecture are a new class of promising supramolecules for future application in nanotechnology because of their exact shape and size, as well as magnetic, photophysical, and electrostatic properties (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). In this article, we describe scanning tunneling microscopy (STM) studies of the self-assembled supramolecular metallacyclic rectangle, cyclobis [(1, ) 2 )anthracene)(1,4Ј-bis(4-ethynylpyridyl)benzene](PF 6 ) 4 , (Fig. 1) (28). The dimensions of a single rectangle molecule were independently determined to be 3.1 nm long by 1.2 nm wide, from the previously reported x-ray crystallographic data (28). The molecular adlayers were prepared on highly oriented pyrolytic graphite (HOPG) and Au(111) surfaces to investigate the effect of substrate on adlayer formation. The molecules self-organize into well ordered 2D adlayers on both surfaces, and high-resolution STM results clearly reveal an intact rectangle on both HOPG and Au (111) surfaces, but the symmetry and molecular orientation the molecules adopt depends on the substrate. Materials and MethodsChemicals. The PF 6 Ϫ salt of the rectangle was prepared analogously to the ClO 4 Ϫ salt previously reported (28), substituting KPF 6 for NaClO 4 .Substrates. HOPG (quality ZYB) was purchased from Digital Instruments (Santa Barbar...

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“…Consistent with sieving behavior that is primarily defined by the cavities contained within individual host molecules, sharp size cutoffs corresponding to minimum cavity sizes are generally observed. (An exception is sieving by the molecular square compound, [Re(CO) 3 Cl( -pyrazine)] 4 , which displays a size cutoff that slightly exceeds the molecular cavity size, but is consistent with the minimum dimensions of crystallographically determined interstitial openings.) Investigations to date have been limited to materials composed of tetrametallic molecular squares; the minimum diameters of the corresponding square cavities range from Ϸ4.5 Å to 23 Å.…”

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confidence: 76%

“…O ver the past dozen years a tremendous number and variety of new cyclic, cavity-containing molecules have been intentionally prepared via metal ion coordination chemistry (1)(2)(3)(4). Interest in these molecules is partly aesthetic (some remarkable high-symmetry, high-mass, polymetallic compounds have been obtained via extraordinarily efficient directed-assembly and related chemical synthesis techniques), and partly practical [cavity-containing assemblies can function as hosts for smaller molecular or atomic (ionic) guests].…”

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confidence: 99%

Shape-selective transport through rectangle-based molecular materials: Thin-film scanning electrochemical microscopy studies

Williams

Benkstein

Abel

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Microporous thin films (Ϸ50 to 400 nm) composed of discrete, cavity-containing molecular rectangles have been prepared. The films, which contain both amorphous and microcrystalline domains, display shape-selective transport behavior. They are permeable to small molecules and to molecules that are short or narrow in at least one dimension-for example, elongated planar molecules-but are impermeable to molecules lacking a narrow dimension. However, the shape selectivity is based on transport through intramolecular rather than intermolecular cavities. By using redox-active probe molecules, rates of transport through the rectangle-based material have been extracted from electrochemical measurements. Spatially resolved measurements obtained via scanning electrochemical microscopy have permitted transport through individual microcrystals to be evaluated semiquantitatively. The measurements reveal that transport is roughly two orders of magnitude slower than observed with thin microcrystalline films of molecular squares featuring similar-sized cavities. The differences likely reflect the fact that cavities within the squarebased materials, but not the rectangle-based material, align to form simple one-dimensional channels.

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Supramolecular Coordination Chemistry and Functional Microporous Molecular Materials

Cited by 319 publications

References 110 publications

Synthesis and photophysical studies of self-assembled multicomponent supramolecular coordination prisms bearing porphyrin faces

Synthesis and photophysical studies of self-assembled multicomponent supramolecular coordination prisms bearing porphyrin faces

Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

Shape-selective transport through rectangle-based molecular materials: Thin-film scanning electrochemical microscopy studies

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